syzbot


INFO: rcu detected stall in sys_clone (2)

Status: upstream: reported on 2025/12/09 09:13
Reported-by: syzbot+7919861b650883ef99d9@syzkaller.appspotmail.com
First crash: 128d, last: 1d11h
Similar bugs (18)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.6 INFO: rcu detected stall in sys_clone 1 C done 8 163d 247d 2/2 fixed on 2025/12/06 23:11
linux-5.15 INFO: rcu detected stall in sys_clone 1 1 862d 862d 0/3 auto-obsoleted due to no activity on 2024/03/15 18:08
linux-6.1 INFO: rcu detected stall in sys_clone 1 3 1009d 1081d 0/3 auto-obsoleted due to no activity on 2023/10/20 18:18
upstream INFO: rcu detected stall in sys_clone (2) mm 1 49 2235d 2352d 0/29 auto-closed as invalid on 2020/06/01 05:26
upstream INFO: rcu detected stall in sys_clone (4) kernel 1 1 1752d 1752d 0/29 auto-closed as invalid on 2021/09/27 17:49
upstream INFO: rcu detected stall in sys_clone (3) mm 1 2 2088d 2110d 0/29 auto-closed as invalid on 2020/10/26 22:48
upstream INFO: rcu detected stall in sys_clone (6) kasan mm 1 1 1423d 1423d 0/29 auto-closed as invalid on 2022/08/23 03:28
upstream INFO: rcu detected stall in sys_clone kernel 1 1 2408d 2408d 13/29 fixed on 2019/10/09 10:54
upstream INFO: rcu detected stall in sys_clone (8) mm 1 C error 403 4d17h 749d 0/29 upstream: reported C repro on 2024/03/29 00:16
linux-4.19 INFO: rcu detected stall in sys_clone 1 2 2306d 2325d 0/1 auto-closed as invalid on 2020/04/21 05:46
upstream INFO: rcu detected stall in sys_clone (5) kernfs 1 5 1557d 1656d 0/29 closed as invalid on 2022/02/08 10:00
upstream INFO: rcu detected stall in sys_clone (7) fs 1 1 1158d 1158d 0/29 auto-obsoleted due to no activity on 2023/05/14 17:18
linux-5.15 INFO: rcu detected stall in sys_clone (2) missing-backport origin:upstream 1 C done 104 6d18h 751d 0/3 upstream: reported C repro on 2024/03/27 00:16
linux-6.1 INFO: rcu detected stall in sys_clone (2) origin:upstream missing-backport 1 C error 60 3d07h 757d 0/3 upstream: reported C repro on 2024/03/20 15:17
android-5-10 BUG: soft lockup in sys_clone 1 1 647d 647d 0/2 auto-obsoleted due to no activity on 2024/10/06 12:58
android-5-10 BUG: soft lockup in sys_clone (2) 1 1 222d 222d 0/2 auto-obsoleted due to no activity on 2025/12/06 02:03
android-5-10 BUG: soft lockup in sys_clone (3) 1 1 74d 74d 0/2 premoderation: reported on 2026/02/01 19:31
android-5-15 BUG: soft lockup in sys_clone origin:upstream 1 C error 18 583d 726d 0/2 auto-obsoleted due to no activity on 2024/12/19 12:14

Sample crash report:
bridge0: received packet on veth0_to_bridge with own address as source address (addr:ae:e9:53:35:1d:19, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	(detected by 0, t=10502 jiffies, g=11185, q=661 ncpus=2)
rcu: All QSes seen, last rcu_preempt kthread activity 10326 (4294958657-4294948331), jiffies_till_next_fqs=1, root ->qsmask 0x0
rcu: rcu_preempt kthread starved for 10326 jiffies! g11185 f0x2 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1
rcu: 	Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
rcu: RCU grace-period kthread stack dump:
task:rcu_preempt     state:R  running task     stack:27656 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x1553/0x45a0 kernel/sched/core.c:6700
 schedule+0xbd/0x170 kernel/sched/core.c:6774
 schedule_timeout+0x188/0x2d0 kernel/time/timer.c:2168
 rcu_gp_fqs_loop+0x313/0x1590 kernel/rcu/tree.c:1667
 rcu_gp_kthread+0x9d/0x3b0 kernel/rcu/tree.c:1866
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 5899 Comm: syz.2.19 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
RIP: 0010:check_kcov_mode kernel/kcov.c:182 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x27/0x60 kernel/kcov.c:216
Code: cc cc cc f3 0f 1e fa 48 8b 04 24 65 48 8b 0d b0 93 7c 7e 65 8b 15 b1 93 7c 7e 81 e2 00 01 ff 00 74 11 81 fa 00 01 00 00 75 35 <83> b9 1c 16 00 00 00 74 2c 8b 91 f8 15 00 00 83 fa 02 75 21 48 8b
RSP: 0018:ffffc900001ef9d0 EFLAGS: 00000246
RAX: ffffffff813b4175 RBX: ffffffff8f0e545c RCX: ffff88802a539e00
RDX: 0000000000000100 RSI: ffffffff8cfa07a0 RDI: 0000000000000004
RBP: ffffc900001efaf8 R08: ffff88802a539e00 R09: 0000000000000008
R10: 0000000000000009 R11: 0000000000000100 R12: ffffc900001efaa8
R13: dffffc0000000000 R14: 0000000000000004 R15: ffffffff8f0e5460
FS:  00007fcc25bd96c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055558cbb77d0 CR3: 000000002e940000 CR4: 00000000003506e0
Call Trace:
 <IRQ>
 unwind_next_frame+0x9b5/0x2970 arch/x86/kernel/unwind_orc.c:521
 arch_stack_walk+0x144/0x190 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0xaa/0x100 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
 __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:329
 kasan_slab_alloc include/linux/kasan.h:188 [inline]
 slab_post_alloc_hook+0x6e/0x4b0 mm/slab.h:767
 slab_alloc_node mm/slub.c:3495 [inline]
 slab_alloc mm/slub.c:3503 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3510 [inline]
 kmem_cache_alloc+0x11a/0x2d0 mm/slub.c:3519
 skb_ext_maybe_cow net/core/skbuff.c:6664 [inline]
 skb_ext_add+0x1b3/0x8e0 net/core/skbuff.c:6738
 nf_bridge_unshare net/bridge/br_netfilter_hooks.c:165 [inline]
 br_nf_forward_ip+0xc6/0x1110 net/bridge/br_netfilter_hooks.c:709
 nf_hook_entry_hookfn include/linux/netfilter.h:144 [inline]
 nf_hook_slow+0xbd/0x200 net/netfilter/core.c:626
 nf_hook include/linux/netfilter.h:259 [inline]
 NF_HOOK+0x23e/0x3e0 include/linux/netfilter.h:302
 __br_forward+0x433/0x610 net/bridge/br_forward.c:115
 deliver_clone net/bridge/br_forward.c:131 [inline]
 maybe_deliver+0xb5/0x150 net/bridge/br_forward.c:191
 br_flood+0x31b/0x670 net/bridge/br_forward.c:237
 br_handle_frame_finish+0x13c5/0x18f0 net/bridge/br_input.c:215
 br_nf_hook_thresh+0x3cd/0x4a0 net/bridge/br_netfilter_hooks.c:1184
 br_nf_pre_routing_finish_ipv6+0x9dc/0xd00 net/bridge/br_netfilter_ipv6.c:-1
 NF_HOOK include/linux/netfilter.h:304 [inline]
 br_nf_pre_routing_ipv6+0x349/0x6b0 net/bridge/br_netfilter_ipv6.c:184
 nf_hook_entry_hookfn include/linux/netfilter.h:144 [inline]
 nf_hook_bridge_pre net/bridge/br_input.c:277 [inline]
 br_handle_frame+0x1245/0x14d0 net/bridge/br_input.c:424
 __netif_receive_skb_core+0xfab/0x3af0 net/core/dev.c:5540
 __netif_receive_skb_one_core net/core/dev.c:5644 [inline]
 __netif_receive_skb+0x74/0x290 net/core/dev.c:5760
 process_backlog+0x391/0x6f0 net/core/dev.c:6088
 __napi_poll+0xc0/0x460 net/core/dev.c:6650
 napi_poll net/core/dev.c:6717 [inline]
 net_rx_action+0x616/0xc40 net/core/dev.c:6853
 handle_softirqs+0x280/0x820 kernel/softirq.c:578
 __do_softirq kernel/softirq.c:612 [inline]
 invoke_softirq kernel/softirq.c:452 [inline]
 __irq_exit_rcu+0xd3/0x190 kernel/softirq.c:661
 irq_exit_rcu+0x9/0x20 kernel/softirq.c:673
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline]
 sysvec_apic_timer_interrupt+0xa4/0xc0 arch/x86/kernel/apic/apic.c:1088
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:qlink_to_object mm/kasan/quarantine.c:138 [inline]
RIP: 0010:qlink_free mm/kasan/quarantine.c:143 [inline]
RIP: 0010:qlist_free_all+0x3f/0xd0 mm/kasan/quarantine.c:185
Code: 00 49 89 f6 48 89 fb 49 bd 00 00 00 00 00 fc ff df 49 89 ef 4d 89 f4 4d 85 f6 75 0b 4c 89 ff e8 c7 04 00 00 49 89 c4 49 8b 2f <49> 63 84 24 c0 00 00 00 49 29 c7 4c 89 e7 4c 89 fe e8 ab e8 ff ff
RSP: 0018:ffffc90004b2f2b8 EFLAGS: 00000282
RAX: ffff888017c4d780 RBX: ffffc90004b2f2f0 RCX: ffffea000073c680
RDX: ffffea0000000000 RSI: 000000000003dc23 RDI: 000000000003dc24
RBP: ffff88802b681e00 R08: 0000000000000001 R09: 0000000000000000
R10: ffff8880617c8b40 R11: fffffbfff2238aa6 R12: ffff888017c4d780
R13: dffffc0000000000 R14: 0000000000000000 R15: ffff88801cf1ab00
 kasan_quarantine_reduce+0x143/0x160 mm/kasan/quarantine.c:292
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:306
 kasan_slab_alloc include/linux/kasan.h:188 [inline]
 slab_post_alloc_hook+0x6e/0x4b0 mm/slab.h:767
 slab_alloc_node mm/slub.c:3495 [inline]
 slab_alloc mm/slub.c:3503 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3510 [inline]
 kmem_cache_alloc+0x11a/0x2d0 mm/slub.c:3519
 ptlock_alloc+0x20/0x70 mm/memory.c:6177
 ptlock_init include/linux/mm.h:2964 [inline]
 pagetable_pte_ctor include/linux/mm.h:2987 [inline]
 __pte_alloc_one include/asm-generic/pgalloc.h:71 [inline]
 pte_alloc_one+0xcc/0x530 arch/x86/mm/pgtable.c:33
 __pte_alloc+0x22/0x2a0 mm/memory.c:438
 copy_pte_range mm/memory.c:1029 [inline]
 copy_pmd_range mm/memory.c:1168 [inline]
 copy_pud_range mm/memory.c:1205 [inline]
 copy_p4d_range mm/memory.c:1229 [inline]
 copy_page_range+0x2d96/0x3670 mm/memory.c:1323
 dup_mmap kernel/fork.c:768 [inline]
 dup_mm kernel/fork.c:1693 [inline]
 copy_mm+0x1281/0x1d80 kernel/fork.c:1742
 copy_process+0x16f7/0x3d80 kernel/fork.c:2507
 kernel_clone+0x24b/0x8a0 kernel/fork.c:2915
 __do_sys_clone kernel/fork.c:3058 [inline]
 __se_sys_clone kernel/fork.c:3042 [inline]
 __x64_sys_clone+0x1b7/0x230 kernel/fork.c:3042
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fcc24d9c819
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fcc25bd8fd8 EFLAGS: 00000202 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 00007fcc25016090 RCX: 00007fcc24d9c819
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 000000002c9a4080
RBP: 00007fcc24e32c91 R08: ffffffffff600000 R09: ffffffffff600000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000000
R13: 00007fcc25016128 R14: 00007fcc25016090 R15: 00007ffc83938d68
 </TASK>
net_ratelimit: 484 callbacks suppressed
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:ae:e9:53:35:1d:19, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:ae:e9:53:35:1d:19, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:ae:e9:53:35:1d:19, vlan:0)
net_ratelimit: 7845 callbacks suppressed
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:ae:e9:53:35:1d:19, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)

Crashes (9):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/04/15 15:40 linux-6.6.y 8cee53b8eaeb c441f497 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in sys_clone
2026/04/05 04:57 linux-6.6.y 08667c1437c0 4440e7c2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in sys_clone
2026/03/28 07:08 linux-6.6.y c09fbcd31ae6 356bdfc9 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_clone
2026/01/25 06:11 linux-6.6.y cbb31f77b879 40acda8a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in sys_clone
2026/01/25 00:50 linux-6.6.y cbb31f77b879 40acda8a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in sys_clone
2026/01/19 18:52 linux-6.6.y cbb31f77b879 a9fc5226 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in sys_clone
2025/12/31 06:17 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_clone
2025/12/12 09:20 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in sys_clone
2025/12/09 09:12 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in sys_clone
* Struck through repros no longer work on HEAD.